Flexible temperature sensor for motor protection



Oct. 27, H. SNOBERGER ETAL 3,537,053

' FLEXIBLE TEMPERATURE SENSOR FOR MOTOR PROTECTION Original Filed Jan.19. 19ss 3 Sheets-Sheet 1 INVENTOR LIP H. SNOBE S RGE'R SELL PHI WILLIAM J. RUS

5' THEIR ATTORNEYS Q 9 P. H. SNOBERGER HAL" 3,537,053

FLEXIBLE TEMPERATURE SENSOR FOR MOTOR PROTECTION Original Filed Jan. 19,1966 s-sheets-sneet z I If IIIIII THEIR ATTORNEYS I P. H. SNOBERGERETALOV "3537,653

FLEXIBLE TEMPERATURE SENSOR FOR MOTOR PROTECTION Original med Jan. 19,1966 Sheets-Sheet s.

INVENTOR v PHILIP H. SNOBERG R WILLIAM J. RUSSELL .THEIR ATTORNEYSUnited States Patent US. Cl. 338-25 8 Claims ABSTRACT OF THE DISCLOSUREA temperature sensor for sensing an overheated condition of theelectrical coil of an electrical motor means or the like to terminatethe operation of a motor means, the temperature sensor including alength of flexible wire encased in a flexible member so as to be adaptedto be disposed between the coil means of the electrical motor to beflexed and compressed thereby Without elongation of the encasing memberso that the resistance of the wire will remain unchanged to accuratelyhave the resistance thereof changed by the change in the temperature ofthe coil means.

This application is a divisional patent application of its co-pendingparent application, Ser. No. 521,591, filed Jan. 19, 1966, now Pat. No.3,422,313, and is assigned to the same assignee to whom the parentapplication is assigned.

This invention relates to an improved temperature sensor.

It is well known that various safety means have been provided in thepast wherein a temperature sensing means is disposed in an electricalmotor to detect a rise in temperature thereof above a safe temperaturelevel during a malfunction in the operatiion of the motor whereby thetemperature sensing means will activate a device to cause the motor tobe turned off before the rise in temperature will adversely affect theelectrical motor.

However, such prior known temperature sensing means normally comprise aresistance wire coiled on a mandrel and being encased in insulatingmeans so that the temperature sensing means can be disposed in the wirecoils of the motor means to detect a rise in temperature thereof throughthe change in resistance of the wire coiled on the mandrel to actuatethe safety device.

These prior known temperature sensing means have various disadvantagesthat will not permit the prior known temperature sensing means to beaccurate for the intended safety purpose thereof.

For example, when the resistance wire is coiled on the aforementionedmandrel, it has been found that a voltage is induced in the resistancewire due to a rapid rate of change in the amperage in the electricalmotor when the rotor thereof has been locked, such amperages being ashigh as 645 amps, whereby such prior known temperature sensor could notbe utilized with a voltage sensitive circuit.

In addition, the prior known mandrel will introduce a temperature lag inthe sensing of the device because the mandrel will act as a heat sink, afeature particularly undesirable because the temperature of amalfunctioning electrical motor will rise to an adverse temperature inabout four seconds or less whereby the detector must operate almostsimultaneously with the rise in temperature to prevent a burn-out of themalfunctioning motor.

Another disadvantage of the the prior known temperature sensor is thatthe resistance wire being utilized is 3,537,053 Patented Oct. 27, 1970the resistance wire during the insertion of the prior known temperaturesensor into the wire coils of the motor, as well as during thesubsequent compressing and compacting of the wire coils of the motorafter the temperature sensing sensor has been placed therein.

Because the prior known temperature sensors are coiled on a mandrel, themass of the temperature sensing wire is substantial and a relativelysmall total surface area of the total wire is responsive to the changesin the temperature of the motor whereby a high degree of accuracy is notpossible.

However, according to the teachings of this invention, a temperaturesensor is provided which eliminates all of the disadvantages of theprior known temperature sensing means, is more accurate for the intendedpurpose, and which can be manufactured in a simple and economical mannerat a substantial savings over the prior known temperature sensing means.

In particular, the temperature sensing means of this invention comprisesa flexible resistance wire encased in and secured to a flexibletape-like member which is adapted to be flexed and compressed withoutelongation thereof so that the resistance of the wire embedded thereinremains the same regardless of the flexed and compressed condition ofthe encasing flexible member.

Accordingly, it is an object of this invention to provide an improvedtemperature sensor having one or more of the novel features set forthabove or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description, which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

FIG. 1 is a perspective view illustrating one embodiment of the improvedtemperature sensor of this invention.

FIG. 2 is an exploded perspective view illustrating the various parts ofthe temperature sensor of FIG. 1.

FIG. 3 is a perspective view illustrating one of the steps in the methodfor forming the temperature sensor of FIG. 1 from the parts illustratedin FIG. 2.

FIG. 4 is an enlarged, fragmentary, perspective view illustrating theterminal lead attaching means of the temperature sensor of FIG. '1.

FIG. 5 is an enlarged, cross-sectional view taken on line 5-5 of FIG. 1.

FIG. 6 is a view similar to FIG. 1 and illustrates another embodiment ofthe temperature sensor of this invention.

. FIG. 7 is a fragmentary, cross-sectional view illustrating the motorprotection means of this invention utilizing the temperature sensor ofFIG. 1.

FIG. 8 is a view similar to FIG. 1 and illustrates another temperaturesensor of this invention.

FIG. 9 is a view similar to FIG. 7 and illustrates the temperaturesensor of FIG. 8 being utilized in a motor protection system of thisinvention.

While the various features of this invention are hereinafter describedand illustrated as being particularly adaptable for providing electricalmotor protection means, it is to be understood that the various featuresof this invention can be utilized singly or in any combination thereofto provide temperature sensing means for other devices as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, one embodiment of the improved temperaturesensor of this invention is generally indicated by the reference numeral10 and comprises a resistance wire 11 encased in and being secured to aflexible tape-like member 12, the resistance wire 11 having the opposdends 13 and 14 thereof respectively interconnected to terminals 15 and16 projecting out of one end 17 of the tape-like member 12. In thismanner, the terminals 15 and 16 are adapted to be interconnected toleads 18 and 19 externally of the tape-like member 12.

The temperature sensor 10 is formed in a unique manner hereinafterdescribed and is adapted to be utilized in a manner illustrated in FIG.7 to protect an electrical motor means 20.

In particular, the motor means 20 of FIG. 7 includes a plurality ofconventional stator windings or wire coils 21 arranged in circularfashion to form the stator means of the motor means 20 about the rotormeans (not shown) of the motor 20. A conventional safety device 22 iscarried by the motor means 20 for sensing the change in resistance ofthe wire 11 of the temperature sensor 10 of this invention, so that whenthe change in the resistance of the wire 11 reaches a particularcondition, the device 22 will turn off the motor means 20'.

The temperature sensor 10 of this invention is adapted to be disposedbetween adjacent coils 21A and 21B of the motor means 20 in the mannerillustrated in FIG. 7 and be interconnected to the device 22 by theaforementioned leads 18 and 19. The temperature sensor 10 is adapted tobe disposed between the coils 21A and 21B during the assembly of themotor means 20 whereby after the sensor 10 has been disposed in thecoils 21 of the motor means 20, the coils 21 are compressed or compactedtogether during the further assembly operation of the motor means 20 andthereby further subject the temperature sensor 10 of this invention to aflexing compressing thereof.

However, the temperature sensor 10 of this invention is so constructedand arranged in a manner hereinafter set forth that regardless of theflexed and compressed condition of the sensor 10, the tape-like means 12will not be elongated so as to subject the resistance wire 11 thereof tothe aforementioned working thereof, whereby the resistance of the wire11 remains the same regardless of the flexed and compressed condition ofthe temperature sensor 10 of this invention. In this manner, thetemperature sensor 10 will be most accurate in its detection of thetemperature change in the motor means 20 during the operation thereof.

Accordingly, it can be seen that if a malfunction occurs in the motormeans 20 during the operation thereof, the rise in temperature of themotor means 20 due to the malfunction will cause a change in theresistance of the wire 11 of the sensor 10 in such a manner that shouldthe resistance of the wire 11 reach a predetermined level, the detector22 will turn off the motor means 20 before the rising temprature of themotor means 20 will adversely affect the same whereby a burn-out of themotor means 20 will be prevented.

The method for making the temperature sensing means 10 of this inventionwill now be described and reference is made to FIGS. 2-5.

As illustrated in FIG. 2, the tape-like means 12 is formed of two strips23A and 23B of a polyimide resulting from the polycondensation reactionbetween pyromellitic dianhydride and an aromatic diamine sold by the I.du Pont de Nemours and Company, Inc., of Wilmington, Del., under thetrade name of Kapton. The strips 23A and 23B can be formed of anysuitable thickness and in the embodiment of the temperature sensor 10 ofthis invention the strips 23A and 23B are each approximately 1 to milsin thickness and have the characteristic that the same can be flexed andcompressed without elongation thereof for the purpose previouslydescribed.

Two strips 24A and 24B of heat sealing means are laminated to the facingsides 25 and 26 of the strips 23A and 23B in any suitable manner. Forexample, the heat lsealing strips 24A and 24B in the embodiment of thisinvention illustrated in FIG. 2 can each comprise a copolymer oftetrafluoroethylene and hexafluoropropylene, sold under the trademark ofPEP-Teflon by E. I. du Pont de Nemours and Company, Inc., of Wilmington,Del.

The resistance wire 11 of the embodiment illustrated in FIG. 2 cancomprise a nickel iron wire of approximately 72% nickel, having adiameter of approximately 0.00ll of an inch, wherein its resistance isabout 105.00 ohms per foot at 20 degrees C. and has a positivetemperature coeflicient of resistance of approximately 0.0045% perdegree C., or 0.0025% per degree F. When such a resistance wire 11 isutilized to provide a circuit of 7 0 ohms, about 8% inches of the wire11 are required.

The wire 11 is bent into the configuration illustrated in FIG. 2 whereina coplanar loop 27 is provided intermediate the ends 13 and 14 of thewire 11. The terminals 15 and 16 are formed from a substantiallyU-shaped blank 17 illustrated in FIG. 2 and are secured to the ends 13and 14 of the wire 11 in any suitable manner to provide electricalconnection therebetween.

The interconnected strips 23A, 24A and 23B, 24B are disposed insuperimposed relation with the wire 11 and terminal blank 17therebetween in the manner illustrated in FIG. 3 and are heat sealed andcompressed together by heat sealing die blocks 28 and 29 in any suitablemanner. For example, the heat sealing operation can take place atapproximately 725 F.

In this manner, not only does the heat sealing means 24A and 24Bsecurely bond the strips 23A and 23B together in superimposed relation,but also the same bond the resistance wire 11 and inner parts of theterminals 14 and 15 between the sheets 23A and 23B, with the wire 11 andinner parts of the terminals 14 and 15 being completely embedded in theheat sealing means 24A and 24B, in the manner illustrated in FIG. 5.

While the heat sealing strips 24A and 24B can be of any suitablethickness, the embodiment illustrated in FIG. 5 is formed with thestrips 24A and 243 being approximately /z mil in thickness.

Therefore, it can be seen that the tape-like means 12 of this inventioncan be formed in a simple and effective manner to encase the wire 11therebetween whereby the wire 11 will not be subjected to theaforementioned working, regardless of the flexed and compressedcondition of the resulting temperature sensor 10 during its assemblywith the motor means 20 previously described, because the tape-likemeans 23A and 23B will not elongate.

Further, it can be seen that the resistance wire 11 of this invention isnot compressed or subjected to tension during the making of thetemperature sensor 10 whereby the resistance of the wire 11 remainsunchanged and can be accurately measured and predetermined.

After the sensor 10 has been formed in the manner illustrated in FIG. 3,the U part 30 of the terminal blank 17, illustrated in dotted lines inFIG. 4, is severed from the terminals 15 and 16 to complete thetemperature sensor 10 of this invention, whereby the leads 18 and 19 canbe subsequently interconnected to the terminals 15 and 16 at theaperture means 31 passing therethrough.

Therefore, it can be seen that the resulting temperature sensor 10 ofthis invention will not be subjected to the aforementioned inducedvoltage due to a locked rotor of the motor means 20 because of thesingle coplanar loop 27 thereof, whereas in the prior known temperaturesensors the resistance wire has many loops coiled upon a mandrel and issubjected to such induced voltages. In addition, no mandrel is utilizedfor the resistance wire 11 of this invention whereby there is notemperature lag in the sensing of the sensor 10, because no mandrelmeans is provided which will act as a heat sink as in the prior knowntemperature sensors.

In addition, the mass of the wire 11 of the temperature sensor 10 ofthis invention is substantially negligible and a large surface area ofthe wire 11 is subjected to temperature variations in the motor means20- so that the response of the wire 11 to temperature changes in themotor means 20 is excellent, whereas in the prior known temperaturesensors a substantially large surface area of the resistance wirethereof is in direct contact with the mandrel carrying the same and notexposed to the temperature of the motor.

Accordingly, it can be seen that the temperature sensor of thisinvention has many improved results over the prior known temperaturesensors, while eliminating all of the disadvantages thereof.

While the temperature sensor 10 of this invention has been previouslydescribed and illustrated as having a single loop 27 in the resistancewire 11 thereof, it is to be understood that the resistance wire 11 canbe disposed in various configuration thereof without changing theadvantages of this invention.

For example, reference is now made to FIG. 6 wherein another temperaturesensor of this invention is generally indicated by the reference numeral100 and parts thereof similar to the temperature sensor 10 previouslydescribed are indicated by like reference numerals followed by thereference letter C.

As illustrated in FIG. 6, the temperature sensor 10C is formed insubstantially the same manner as the temperature sensor 10 previouslydescribed in that the resistance wire 11C is encased in and secured tothe flexible tape-like means 120 formed in the manner previouslydescribed with the opposed ends 13C and 14C of the resistance wire 11Cbeing interconnected to the terminal means 150 and 16C for the purposepreviously described.

However, the resistance wire 11C of the sensor 10C is provided with aplurality of loops '32, 33 and 34 to define a substantially M shapethereof to permit the length of the wire 11C to be substantially longerthan the wire 11 previously described, while the overall length of thesensor 10C is substantially the same as the sensor 10 previouslydescribed. However, it can be seen that the loops 32, 33 and 34 of theresistance wire 11C are all coplanar with each other and with thetape-like means 12C, so that there will be no compacting and workingthereof for the reasons previously described.

In addition, it may be found desirable to provide a relatively longtemperature sensor according to the teachings of this invention whichcan be completely passed through the motor means.

For example, reference is now made to FIGS. 8 and 9 wherein anothertemperature sensor of this invention is generally indicated by thereference numeral 10D and parts thereof similar to the temperaturesensor 10 previously described are indicated by like reference numeralsfollowed by the reference letter D.

As illustrated in FIG. 8, the resistance wire 11D comprises a continuouslength without any loops therein and being interconnected to terminalmeans D and 16D at the opposed ends 13D and 14D thereof, with theterminal means 15D and 16D projecting from the opposed ends 17D and '35of the encasing and securing flexible tape-like means 12D.

In this manner, the temperature sensing means 10D of this invention canbe passed through the motor means 20D in the manner illustrated in FIG.8 so that the temperature sensing means D completely extends around andthrough the stator coils 21D, with the ends '35 and 17D of the sensor10D being disposed closely adjacent each other and being interconnectedto the detector 22D by the leads 18D and 19D respectively interconnectedto the terminals 15D and 16D in the manner previously described.

Accordingly, it can be seen that the temperature sensors of thisinvention can have various configurations for particular purposesthereof, with each temperature sensor of this invention having theaforementioned advantages while still eliminating the previouslydescribed disadvantages of the prior known temperature sensing means.

Accordingly, it can be seen that this invention provides an improvedtemperature sensor.

What is claimed is:

1. A temperature sensor comprising a length of flexible wire adapted tohave the resistance thereof changed by the change in temperaturethereof, and a flexible member encasing and being secured to said wire,said encasing member being adapted to be flexed and compressed withoutelongation thereof whereby the resistance of said wire remains unchangedregardless of the flexed and compressed condition of said encasingmember, said wire having opposed sides respectively secured to saidflexible member and being disposed in two flat planes throughout thelength of said wire in said encasing member with the distance betweensaid planes being substantially equal to the transverse cross-sectionalthickness of said wire.

2. A temperature sensor as set forth in claim 1 wherein said wire has acoplanar loop therein.

3. A temperature sensor as set forth in claim 2 wherein said flexiblemember is normally in flat tape-like form and said wire and loop thereofare coplanar with said flexible member.

4. A temperature sensor as set forth in claim 1 and including twoterminal means respectively secured to the opposed ends of said lengthof wire.

5. A temperature sensor as set forth in claim 1 wherein said flexiblemember comprises two tape-like strips superimposed on each other andholding said wire therebetween, said tape-like strips providing flatopposed surfaces for said sensor.

'6. A temperature sensor as set forth in claim 5 wherein each stripcomprises a polyimide resulting from the polycondensation reactionbetween pyromellitic dianhydride and an aromatic diamine.

7. A temperature sensor as set forth in claim 6 wherein heat sealingmeans heat seals said strips together in said superimposed relation withsaid wire being embedded in said heat sealing means.

8. A temperature sensor as set forth in claim 7 wherein said heatsealing means comprises two strips of a copolymer of tetrafluoroethyleneand hexafiuoropropylene laminated respectively to the inner sides ofsaid firstnamed strips.

References Cited UNITED STATES PATENTS 2,569,714 10/1951 Gregory 338-26X 2,717,945 9/1955 Dresios et al. 338-26 RODNEY D. BENNETT, 111.,Primary Examiner M. F. HUIBLE'R, Assistant Examiner U.S. Cl. X.R.338-26, 212

